Declines in cognitive function and mobility are common in older adults, arising from the collective impacts of subclinical pathologies and chronic disease across multiple organ systems. As these declines progress from minor functional limitations to more severe stages of Alzheimer?s disease and related dementias and physical disabilities, there can be substantial impairments to self-care activities and independent living. This leads to poorer quality of life as well as significantly increased health care costs for long-term services and support. Unfortunately, individual-level prevention efforts have been largely ineffective in reducing the population prevalence of disability and only modestly successful for Alzheimer?s disease and related dementias. Our central hypothesis is that particulate matter (PM) and ozone (O3) air pollution are likely, but largely unexplored, environmental risk factors that could be controlled on the population-level to minimize cognitive and mobility declines in older adults. This hypothesis is based on evidence that air pollutants enter the blood stream, translocate into the brain, and initiate systemic pathophysiological processes that lead to subclinical, preclinical, and then, chronic disease in multiple organs. This accumulation of subclinical and clinical disease ultimately results in an increased risk of cognitive and mobility impairments, Alzheimer?s disease and related dementias and physical disabilities, and health care costs due to lost independence. To test our hypothesis, we will newly predict exposures to ambient PM and O3 for each Health and Retirement Study (HRS) respondent using state-of-the-art national exposure models while also accounting for non-ambient sources of exposure. The HRS is a nationally-representative cohort of over 37,500 older adults followed for more than 20 years with detailed biennial data on cognitive function, Alzheimer?s disease and related dementias, mobility, disability, and health care expenditures. Specifically, we aim to: 1) Prospectively examine associations of long-term exposures to fine (PM2.5) and coarse particulate matter (PM10-2.5) and O3 in ambient air with cognitive and mobility declines in older adults, 2) Directly estimate associations between long-term exposures to PM2.5, PM10-2.5, and O3 in ambient air and health care costs due to lost independence in older adults, 3) Quantify the cognitive and mobility-related health and economic burdens attributable to long-term exposures to ambient PM2.5, PM10-2.5, and O3 among all older adults in the US, and 4) Create and disseminate open-access resources of ambient PM2.5, PM10-2.5, and O3 exposures for the HRS and estimates of county-level and national health and health care cost burdens due to PM and O3?s impacts on cognition, Alzheimer?s disease and related dementias, mobility and physical disabilities for the entire US. This research is expected to have a large public health impact by providing evidence to policy makers and stakeholders at the local, state, and national levels about a novel, environmental risk factor that could be modified at the population-level to promote health in older ages.